This invention relates to analytical apparatus and the methods for analytical monitoring of liquids, and further relates to the preparation of water in a condition free of ions of a certain selected species.
A requirement which frequently arises in relation to plant using or treating certain liquids is that the plant operator should know or have means for ascertaining the concentration of chemical species present in the liquid being treated or processed. There may be many reasons why the need for this information arises, for example the need for quality control of a particular product, or the need for checking the presence of corrosion-inducing species or the need for economy in the use of expensive additives to certain process liquids. Where the concentrations of interest fall below, or at the lower end of, the measuring range of conventional analytical instruments, difficulties arise in providing the plant operator with the data he needs and he remain unaware whether corrective action is necessary. One such difficulty arises in the monitoring of corrosion and stress corrosion cracking of stainless steel components by chloride species in high pressure boiler systems where it is important that any chlorides should be at a very low level. It is our experience that the chloride level in the feed water is already below the limit of detection by the on-stream colorimetric method and the requirement exists for monitoring even lower levels than are measurable by this means.